1. Field of the Invention
This invention generally relates to drainage valves used in underground watering systems that when shut off, automatically drain the water from the drainage valve and the underground system to prevent damage due to freezing ground conditions and, more particularly, to drainage valves used in systems where the water supply is abruptly shut off.
2. Description of the Prior Art
My U.S. Pat. No. 3,779,276 shows a drainage valve for an underground watering system. The drainage valve includes a resilient valve member that prevents water from escaping from the underground water system under high line pressures but opens under lesser shutoff pressures to permit the water in the drainage valve and the underground water lines to drain into the soil. While my prior art drainage valve effectively drains the water from the system and prevents subsoil water from entering the line, the resilient valve member in my drainage valve may be blown out by high pressure water line surges occurring during shutoff. Typically, in most underground systems the water pressure fluctuates as valves are opened or closed. In a zone type system where an electro-mechanical valve is used to shut off the water supply, the rapidity of the closing action of the valve creates high pressure surges that may blow out the resilient valve member thereby rendering the drainage valve ineffective. Because the drainage valves are located underground, it may be some time before the faulty drainage valve is found and replaced. Usually the only way a faulty drainage valve can be discovered is to observe the area around the drainage valve to see if the ground is excessively wet. Since the systems are located underground and are not disturbed once installed, one of the difficulties is the inability of the user to determine that the system has a failure until the ground becomes saturated. My present invention solves the problem of resilient valve member blowout yet provides a drainage valve that functions to drain water from the valve while preventing subsoil water from entering the systems.